A traditional power tool comprises a gear train driven by a separate motor, the gear train and motor being installed in a case of the power tool independently. Alternatively, the motor and gear train may be connected together before being fitted to the case. In either assembly method, eccentricity inevitably exists between the gear train and the motor.
Eccentricity between the gear train and the motor means that the alignment between the motor shaft and the gear train is not correctly aligned increasing the friction of the connection resulting in higher friction and greater heat generation. This higher friction means that the power tool has a lower efficiency and will use more power to do the same task. This is undesirable, especially if the power tool is powered by batteries.